The present invention relates to a hydrokinetic coupling apparatus, especially for a motor vehicle, of the type which is described and shown for example in the document WO-A-93/13339 or the document EP-A-0 612 384.
That document describes and shows a hydrokinetic coupling apparatus, especially for a motor vehicle, of the type comprising:
a casing having a generally transversely oriented wall which is adapted to be coupled in rotation to a driving shaft;
a turbine wheel which is fixed in rotation to a hub which is adapted to be coupled in rotation to a driven shaft;
a lock-up clutch interposed operatively between the turbine wheel and the transverse wall which comprises, arranged axially from front to rear between the turbine wheel and the transverse wall:
a damper plate which is fixed to the turbine wheel for rotation therewith and is in the form of a generally transversely oriented annular ring having at its outer periphery a generally axially oriented annular portion which circumferentially guides and retains circumferentially acting resilient members, and which includes generallyxe2x80x94transversely oriented zones of engagement for the circumferential ends of the resilient members;
a piston in the form of a flat annular ring, oriented generally transversely, movable axially and coupled in rotation to the casing;
and at least one flat annular friction disc, oriented generally transversely and carrying, on its opposed front and rear faces, two annular friction liners which are arranged to be gripped axially by the piston between, respectively, itself and the internal face of the transverse wall of the casing which is in facing relationship to it, the friction disc including, at its outer periphery, drive lugs which extend axially towards the rear inside the peripheral annular portion of the damper plate, so that each of them is received between the circumferential ends of two consecutive circumferentially acting resilient members, and which is movable axially with respect to the damper plate.
The document FR-A-2 635 845 describes and shows an apparatus of the same type in which a torsion damper is interposed between the hub of the turbine and the piston, while the friction disc is in mesh with the outer periphery of the casing. In that document, the damper is arranged generally radially inwards, radially inward of the central portion of the turbine wheel having the largest axial dimension.
The invention aims to propose an apparatus of the type described above, in which its axial size is reduced and in which the main components are of simple forms, easy to make.
With this in view, the invention proposes hydrokinetic coupling apparatus, in particular for a motor vehicle, of the type comprising:
a casing having a generally radially oriented wall and adapted to be coupled in rotation to a driving shaft;
a turbine wheel coupled in rotation to a hub which is adapted to be coupled in rotation to a driven shaft;
a piston, in the form of a generally radially oriented annular ring movable axially and coupled in rotation to the casing;
and a generally radially oriented annular friction disc adapted to be gripped axially by the piston between, respectively, itself and the facing inner surface of the radial wall of the casing,
characterised in that the friction disc is coupled at its radially inner periphery to the hub of the turbine wheel, and in that the piston has means at its radially outer periphery for meshing with a radially outer peripheral portion of the casing.
Thanks to the invention, the friction disc is simplified, and the axial size of the hydrokinetic coupling apparatus is reduced at its outer periphery.
In accordance with further features of the invention:
the turbine wheel, the piston, the friction disc and the radial wall of the casing are arranged in axial succession from front to rear, which enables the turbine and impulse wheels to be given the desired form;
the turbine wheel is coupled in rotation to a stepped hub which comprises a front portion of larger diameter for guiding the radially inner periphery of the piston, and a rear portion of smaller diameter to which the inner periphery of the friction disc is coupled in rotation;
the radially inner periphery of the piston is configured as a sleeve which is guided in sealed sliding movement along the outer periphery of the front portion of the hub of the turbine;
the friction disc is in the form of a flat annular ring, which simplifies its manufacture;
the inner periphery of the friction disc is coupled rigidly to the hub of the turbine;
the friction disc is coupled to the radially inner periphery of the hub of the turbine with a torsion damper interposed, so that the said damper can be relatively thick in the axial direction since it is arranged in the lower or radially inner, part of the apparatus;
the torsion damper includes a damper plate in the form of a flat annular ring which is coupled at its radially inner periphery to the hub of the turbine;
the friction disc and the damper plate are substantially coplanar, so as to give good transmission of forces and good working conditions;
the radially inner periphery of the damper plate is configured as a splined guide sleeve through which the splined rear portion of the hub of the turbine, along which the sleeve is mounted for sliding movement, extends;
the radially inner periphery of the damper plate is coupled axially and in rotation to an internally splined central guide sleeve through which the splined rear portion of the hub of the turbine, along which the sleeve is mounted for sliding movement, extends;
the radially inner periphery of the damper plate is splined internally, and the splined rear portion of the hub of the turbine, along which the damper plate is mounted for sliding movement, extends axially through the latter;
the piston includes, considered radially outwards from the inside, an internal peripheral portion and a bent first intermediate portion which substantially follows the external profile of the hub and the turbine wheel, then an intermediate second portion in the form of a radially oriented flat ring, the rear annular face of which is in facing relationship with a friction ring, and an outer peripheral portion in the form of a generally axially oriented skirt which includes means whereby it can mesh with a radially outer peripheral portion of the casing, so that the turbine wheel can be given a semicircular form in cross section;
the outer peripheral skirt extends axially forward from the second intermediate portion;
the outer peripheral skirt portion is a tubular cylindrical skirt;
the outer peripheral skirt is a frusto-conical skirt;
the piston has fluid passage holes;
the passage holes are formed in the bent junction zone between the intermediate second portion and the outer peripheral skirt;
the passage holes are formed in the outer peripheral skirt;
the radially outer periphery of the casing with which the piston meshes is generally tubular and cylindrical;
the radially outer periphery of the casing delimits an internal cylindrical surface for centring the radially outer periphery of the piston, and the hub of the turbine extends with a radial clearance through the radially inner periphery of the piston;
the piston has a generally radially oriented outer peripheral portion, the cylindrical free edge of which is centred in the internal cylindrical centring surface of the casing;
the outer peripheral skirt portion of the piston includes a set of bosses formed in relief, which extend radially outwards and are centred in the internal cylindrical centring surface of the casing;
the outer peripheral portion of the piston has a set of lugs or splines spaced apart circumferentially and received in complementary notches or splines in the tubular periphery of the casing;
the complementary notches or splines in the tubular periphery of the casing are formed in an annular member which is fixed internally in the casing;
the annular member is a starter crown;
the casing is made as two complementary half shells, namely a front half shell and a rear half shell, each of which includes a portion of the tubular periphery of the casing;
the complementary notches or splines in the tubular periphery of the casing are formed in one of the two portions of the tubular periphery of the casing;
the annular member is fixed within one of the two portions of the tubular periphery of the casing;
the apparatus includes a torsion predamper which is interposed between the turbine hub and the main damper, so as to give improved vibration absorption;
the predamper is radially adjacent and close to the hub;
the predamper is disposed axially between the piston and the main damper;
the predamper is disposed axially between the main damper and the transverse wall, in facing relationship with it, of the casing.
Thanks to the invention, the turbine and impulse wheels may have in cross section either a semicircular or an ovoid form.
The friction disc carries at its radially outer periphery two friction liners on its opposed transverse faces.